1. Field of the Invention
The present invention is generally in the field of electronic circuits and systems. More specifically, the present invention is in the field of communications circuits and systems.
2. Background Art
In the field of wireless communications, the challenge of managing the timing of communications between a peripheral device and a primary device has traditionally been addressed using one of two conventional approaches. In the first conventional approach, a peripheral device controls the timing of the communication, while in the second conventional approach a primary device controls the timing. All such systems generally must deal with “clock drift”, where the clocks of the primary device and the peripheral device slowly move out of sync with one another. If both the primary device and peripheral device have a ±100 ppm crystal, for example, there can be a clock drift of up to ±200 ppm between the two devices. This means that a primary device, in combination with a peripheral device transmitting at a 1 second interval, would have to begin listening up to 200 μs before the time at which it expects the peripheral device to transmit.
According to the first conventional approach to controlling the timing of the primary and peripheral devices, the peripheral device transmits a signal to the primary device, and the primary device tracks the timing of the peripheral device's transmissions. This approach can be either one-way or two-way. In the case of a one-way communication, the peripheral device simply transmits and does not wait for a response. The primary device must typically begin “listening” a little earlier than when it expects the peripheral device to transmit in order to compensate for any possible clock drift. As a result, the primary device draws more power due to this additional “listening” period. In the case of a two-way communication, the primary device can acknowledge the receipt of the data. If the primary device does not receive the data, the peripheral device can keep trying. This improves robustness, but increases power consumption in both the primary and peripheral devices.
In a second approach, the primary device controls timing and the peripheral device wakes up to be polled by the primary device. With this approach, the burden of compensating for clock drift rests on the peripheral device, which must be prepared to listen early for a polling signal, due to clock drift. Since the peripheral device is often a small, battery-powered device, this is undesirable as the receive period must typically grow as the communication interval increases, hence negating some of the reduction to average power consumption achieved by lengthening the communication interval. Using more accurate crystals on the peripheral and primary devices can help, but increases system costs.
Thus, there is a need to overcome the drawbacks and deficiencies in the art by providing a solution which allows lower power consumption to be achieved in a peripheral device while allowing a primary device to more efficiently manage radio traffic with a plurality of devices, including the peripheral device.